A telephone number within the North American Numbering Plan (NANP) is defined as a 3-digit area code, followed by a 3-digit central office code, followed by a 4-digit line number.
Telephone numbers that begin with the same 3-digit area code are referred to as “being in the same area code” or “having the same area code.” Typically when the originating and destination telephone numbers are both in the same area code, a telephone number can be dialed using only the 3-digit central office code followed by the 4-digit line number—this is known as the “7-digit telephone number,” and is used for what is known as “7-digit dialing.” If the originating and destination telephone numbers are not in the same area code, then the area code must be included when dialing—this is known as “10-digit dialing,” because it uses the full 3-digit area code+the 7-digit telephone number. Historically, a single area code would be assigned to a specific geographic region, creating a framework where all telephone numbers allocated within that geographic region would begin with the same 3-digit area code. These geographic regions together with their associated area codes are often referred to as Numbering Plan Areas, or NPAs. The definition of an NPA taken from the Alliance for Telecommunications Industry Solutions (ATIS) website is as follows:                numbering plan area (NPA): A defined geographic area identified by a unique three-digit code used in the North American Number Plan Area. [T1.207-1998] [T1.209-1998] Note 1: Defined geographic area could mean the entire area encompassed by the North American Numbering Plan Area (for 800, 888, 877 codes, etc.). Note 2: By virtue of the overlay concept deployed in some states, there may be two (or more) NPAs assigned to the same defined geographic area.        
Because every telephone number within a specific NPA always began with the same 3-digit area code, the architects of the telephone network took advantage of this characteristic, and designed dialing patterns which enabled calls to be made within a single NPA by dialing just the 3-digit central office code followed by the 4-digit line number, or in other words, just the 7-digit telephone number. Dialing the area code was unnecessary for these types of calls because the telephone network was programmed to assume that if only the 7-digit portion of a telephone number were dialed, then both the originating and the destination telephone numbers began with the same area code. This 7-digit dialing pattern became ubiquitous throughout the NANP for local calls within a single area code. Customers became familiar with this 7-digit pattern because, until recently, it was the main way that most local calls were dialed. Clearly, since it requires less effort to dial 7-digits compared to 10-digits or 1+10-digits, many people have become attached to dialing 7-digits for phone calls when possible, and in fact prefer it.
At least two factors have put pressure on the ability of a user to continue dialing/entering/specifying 7-digits to make telephone calls. One of those pressures comes from the telecommunications industry's “Industry Numbering Committee” (INC) in a proposal called the “Uniform Dialing Plan.” This plan promotes the idea of doing away with 7-digit dialing altogether, in favor of dialing all calls using the full 10-digits. The INC's proposal argues that it would be beneficial if all phone calls were dialed with the same 10-digit pattern, regardless of whether the originating and destination phone numbers were in the same area code. Although this proposal would provide certain benefits (in the form of simplified administration for phone companies, and a consistent method of dialing for everyone using the telephone system), customers would be forced to update equipment, reprogram auto-dialers, change databases, and dial 3 or 4 extra digits for every phone call. In the case of having to dial the 3-digit area code along with the 7-digit telephone number, the result would be 43% (3/7) more digits than for a 7-digit call alone, and in cases where a “1+” the 3-digit area code is required the result is that customers have to dial 57% (4/7) more digits. So, for the consumer, the change to 10-digit or 1+10-digit dialing requires extra effort and leads to wasted time and potential frustration. This is especially so if a wrong number is dialed and the user then has to redial from scratch. For example, not limitation, if a caller dials 7-digits, but 1+10 digits are required, the caller will have to hang up and redial. After doing so, the caller will have dialed 18 digits to complete the call.
The other factor which has put pressure on 7-digit dialing comes from the fact that in the past decade it has been necessary to introduce many new area codes to keep up with the demand for new telephone numbers. Historically, a new area code would be introduced by splitting an existing Numbering Plan Area (NPA) roughly in half geographically, keeping the original area code for all of the telephone numbers that are located in one half, and changing the area code for all of the telephone numbers in the other half—the result is two geographically-smaller NPAs, each with their own area code. This method is disruptive because customers who get the new area code lose their original 10-digit phone numbers. Since the 7-digit portion of their phone number remains the same, customers within each of the new NPAs can still make calls within their own NPA by dialing the same 7-digits they used in the past. However, they can no longer use just 7-digits to make calls across the newly-defined line where the original area code was split—those calls will require dialing the full (1+) 10-digit number. In addition, callers in area codes outside of the original NPA, will have to use the new area code to connect with customers whose 10-digit numbers changed as a result of the new area code. And because it is not always obvious to the caller that he is calling someone who got the new area code (or that an area code split even happened in the first place), there is additional disruption and confusion.
Recently, a new method for introducing new area codes has been implemented in several NPAs. This new method is called an area code overlay. With overlays, instead of creating two new NPAs out of an existing NPA, the new area code is simply laid on top of the existing Numbering Plan Area. Thus both area codes occupy the same region, nobody has to give up their existing phone number, and the disruption that comes from the re-distribution of 10-digit telephone numbers is eliminated. However, a different kind of disruption occurs in overlays. Due to certain technical and regulatory issues related to overlays, 7-digit dialing in these regions is impractical and has been disabled by the phone companies. This is unfortunate because even though the 7-digit dialing pattern no longer functions within overlay areas, people and automatic dialing devices will often attempt to dial telephone numbers without first dialing the area code. With people, the reason for misdialing by using a 7-digit telephone number is often because of habit or a lack of knowledge about the new dialing pattern, and with automatic dialing devices the reason is because the devices have been previously programmed with only the 7-digit telephone number. The disruption to the 7-digit dialing pattern is a source of frustration for customers, and for phone companies, results in significant wasted network resources that must be allocated to deal with 7-digit misdials. (For example, the network first has to determine that the 7-digits it received are a “misdial,” then the network has to provide an announcement describing how to redial, the current network/user transaction has to be terminated, a new network/user transaction has to be initiated, and then the network has to receive and interpret the new (1+) 10-digits that the user dials.) Additionally, this disruption to the established 7-digit dialing pattern results in a cost of time and money that is needed to update and/or reprogram customer equipment such as PBXs, auto-dialers, security dialing systems and the like.
The need for a solution that would mediate the problems caused by disruption to established 7-digit dialing patterns can be seen in the following discussion: In situations where an area code is required for dialing, if a 7-digit telephone number is dialed by mistake, the user typically hears a message instructing him or her to hang up and redial using the area code plus the 7-digit telephone number. So, instead of the three extra digits (for the area code) that the customer forgot to enter to begin with, he or she has to hang up and redial the complete 10-digit number, which along with his or her original 7-digit misdial is 70% (7/10) more digits than if the 10-digit number had been dialed correctly to begin with (and 143% (10/7) more digits than if 7-digit calls could still be made in this situation). Clearly, this can be quite time consuming and frustrating for customers, and it is especially difficult for people with certain physical disabilities, the elderly, and young children, who may find it difficult to dial a telephone to begin with. With automatic dialing devices the situation is even worse, since the machine cannot hang up and redial in the correct manner.
One solution for minimizing this disruption can be found in applicant's previous U.S. Pat. Nos. 6,061,443; 6,343,125; and 6,687,365 together with pending U.S. application Ser. No. 10/707,956, which are hereby incorporated by reference and included in the cross reference to related applications herein. These patent documents disclose a method and apparatus for dialing 10-digit phone numbers while entering the fewest possible digits, using a limited selection of (ten or eleven) area codes for any given implementation. The objective is to preserve as much as possible of the look and feel of the previously-established dialing pattern for a region. Specifically, the foregoing allow users to select from a list of pre-designated area codes after having entered/dialed/specified a 7-digit number. In the foregoing, a single extra digit—or even the absence of a digit after a timing delay pause, or in other embodiments, without the timing delay pause—allows the user to select the appropriate area code, and thus complete the call with minimal additional keystrokes (one or none).
In contrast to the foregoing, it would be desirable to provide a method and apparatus to specify any area code in response to a determination that an area code is missing, but is required to complete the call. Particularly, it is desirable that there be no limitation on the number of area codes which are available to choose from (simply enter the entire area code without being restricted to a pre-designated set of area codes), and no need to designate a list of selectable area codes beforehand.
It is further desirable to provide a method and apparatus which enables correction of a misdialed number—particularly one for which the omission or misdialing of an area code is the error—without re-keying the digits which have already been dialed. This type of dialing error will become more frequent as disruption to established dialing patterns spreads, as a result of area code splits, overlays, the INC's “Uniform Dialing Plan,” or any other change that affects the way that telephone numbers have traditionally been dialed.